What does Genesis 25:31 mean?

Esau, declaring himself exhausted after working in the field, has requested some of Jacob's red stew (Genesis 25:29–30). Jacob smells an opportunity or perhaps, understanding his brother's lack of self-control, he has set this whole thing up ahead of time. Jacob seeks to make a deal. He says simply, "Sell me your birthright."

The birthright, or "firstborn rights," gave the firstborn son special privileges. For one thing, the firstborn was often entitled to a double share of the father's property when he died. The birthright may have come with other privileges, as well. Jacob is demanding a huge price for a bowl of stew.

Esau may have thought this was a joke at first. Even when Jacob doubles down on his request, demanding that Esau swear an oath (Genesis 25:33), it's possible he didn't take the situation seriously. Jacob clearly does, however. And, he'll perform an even more daring act of trickery later on (Genesis 27). Esau's careless reaction costs him dearly.